The oxidation-reduction proteins, azurin, cytochrome c551 and cytochrome oxidase all from Pseudomonas aeruginosa are being studied from several points of view. The existence of a complex between azurin and cytochrome oxidase is going to be checked by a fluorescence titration, by high resolution NMR studies and by a picosecond kinetics experiment. The strength of the complex has bearing on the interpretation of T-jump studies of the oxidation-reduction reaction Azurin (II) plus Cyt c551 (II) equals Az(I) plus Cyt c551 (III) which are being carried out. Interheme electron transfer is being studied in the four heme protein cytochrome oxidase by pulse radiolysis. It is hoped to crystallize cyt c551 and to measure its ESR spectrum at low temperature; the purpose is to determine the orientation of the principal axes of the g tensor with respect to the molecular axes and to compare with mammalian cytochrome c which has different g-values and proton hyperfine interactions.